Based on micro electro mechanical systems, microfluidic chip is a technique that microconduit forms a network on chip and controllable microfluid completes all kinds of biological and chemical processes throughout the whole system. In the early days of microfluidic chip, the chip capillary electrophoresis is the mainstream technology and the chip has simple structure and single function; in recent years, the microfluidic chip develops towards functionalization and integration rapidly, for example, DNA amplified reaction, immunoreaction, cell lysis and other important biological and chemical processes have become new hotspots. It needs to make a large number of independent and homogeneous microcells on chip to study these complex biochemical reactions and all microcells together make up a microreactor array.
There are two steps in constructing a microreactor array: step one, distribute the reagent to construct a large number of uniform microcells (see FIG. 1); step two, use a valve or medium to isolate the microcells and guarantee the homogeneity and independence of each microcell. For step one, there are a variety ways of reagent distribution at present, such as hydrophilic conduit type (CN1996009B), vacuum negative-pressure type (CN101590389A), centrifugal type (U.S. Pat. No. 6,627,159, US20050199500A1, US6919058B2, US20030166265A1, WO9533986A1), etc. For step two, the isolation mode of microcells is limited, only including conduit deformation isolation (U.S. Pat. No. 6,627,159), mineral oil/silicone oil isolation (CN101590389A) and natural air isolation.
Conduit deformation isolation uses external equipment to deform the metal substrate with pressure sensitive adhesive (PSA) and then blocks up the flow path. The drawback of this approach is that it cannot be automatical and has restrictive requirements for the material of chip substrate, and the composition of PSA may interfere with the reactor. Mineral oil isolation refers to add mineral oil after reagent distributing, and isolate by the difference in surface tension of oil and water. The drawback of this approach is that the user shall add samples two times, and because of the adhesive tape is often used to seal inlet and outlet of the chip so the mineral oil may erode the adhesive tape causing reagent leakage and environmental pollution.
Natural air isolation is that the original main channel changes into air after reagent distribution and uses the natural air space for isolation. The approach is easy to use and has a simple principle, but its drawback is also the most prominent. In actual use, the temperature of the chip containing microcells is generally controlled as a whole, however different areas of the chip are different in material and structural which cause the liquid in microcells to gradually evaporate and condense in the main channel which does not have liquid, and the condensed liquid droplets will gradually extend and form a liquid film. The evaporation firstly lead to different degrees of reagent reduction of each reaction cell, it damages uniformity of each microcell (see FIG. 2); The liquid film will connect each microcells resulting in cross contamination and damaging the independence of each microcell (see FIG. 3).